The present invention relates to methods of making molded articles from a lightweight cementitious composition and in particular, to a method of making an article from a cement and perlite composition, and a hollow, decorative article made therefrom.
Many property owners have sought to conceal unsightly utility installations, such as water well heads, septic vent stacks, telephone junction boxes, and buried gas tank hatches. Existing concealment devices, such as plantings, planters, and well houses have provided only partial or seasonal concealment of the utility installations. Such existing concealment devices are also not sufficiently weatherproof and are susceptible to damage caused by sun, rain, ice, and wind. Other concealment devices, such as well houses, are large heavy structures that are difficult to install and remove and could also present a hazard individuals nearby.
A device is needed that will adequately conceal utility installations in all seasons while providing an aesthetically pleasing appearance that blends with the natural surroundings. A concealment device is also needed that is structurally sound and weather resistant to withstand sun, rain, snow, ice and wind while being sufficiently light weight to be easily installed and moved. Furthermore, a concealment device is needed that can be made with various different shapes and surface ornamentation""s. Additionally, there is also a need for lightweight outdoor decorative objects such as posts, birdbaths, etc., that are aesthetically pleasing, yet can be purchased, moved and installed by a typical homeowner, without need for a heavy duty truck or similar delivery vehicle or heavy installation equipment.
Cementitious compositions are commonly used to form structures and articles in the building industry. Although cementitious compositions, such as concrete or cementitious compositions including other aggregates, are desirable in terms of price and weather resistance, the use of cementitious compositions to form a decorative article or a concealment device for covering utility installations presents a number of other problems related to the physical characteristics of the material and the methods of using the material.
Using concrete, for example, to form a generally hollow article for covering utility installations results in an article that is heavy and difficult to install or move. To minimize the weight of a hollow article made from concrete, the thickness of the walls of the article would have to be dangerously thin, thereby sacrificing the structural integrity of the article. Molding structures or articles from concrete is also labor intensive. Concrete is thus difficult to form into a lightweight article having various decorative shapes and does not provide a decorative surface texture or appearance.
Lightweight cementitious compositions including perlite, a siliceous volcanic rock which has been expanded by heating, have been used in the building construction field as a lightweight insulating concrete for roof decks, floor systems, sound/firewalls, and other insulating applications. However, the prior art does not disclose the use of a lightweight cementitious composition to cast a hollow, decorative article with various shapes and surface textures. Typical perlite concrete compositions also do not provide sufficient strength and weatherability.
Accordingly, a need exists for a hollow, decorative article that is made from a cementitious composition and is lightweight, easily installable, weather-resistant, easily molded to a desired shape, for example a shape that conceals a utility installation, and has a decorative shape and surface texture. A need also exists for a method of making such an article from a lightweight cementitious composition by casting the article with various shapes, surface textures and other decorative features.
The present invention features a novel method for making an article from a cementitious composition and also features a hollow, decorative article made according to the method. The method comprises the steps of: mixing a castable cementitious mixture including an aqueous slurry of at least cement and perlite; transferring a quantity of the castable cementitious mixture into a mold having an internal mold form and an external mold form; maintaining the castable cementitious mixture between the internal mold form and the external mold form until the castable cementitious mixture at least partially cures to form the article; and removing the external mold form and the internal mold form from the article. The preferred method includes inserting an internal mold form into the external mold form and the quantity of the castable cementitious mixture, for displacing the quantity of the castable cementitious mixture between the internal mold form and the external form. One method of making a decorative article from a cementitious composition further includes one or more steps of finishing the surface of the molded article, such as by carving.
The preferred cementitious mixture includes portland cement and a perlite/cement ratio of about 4:1 by volume. The castable cementitious mixture also preferably includes an air-entraining agent, for entraining air bubbles, improving mixability and reducing a density of the castable cementitious mixture to facilitate displacement of the castable cementitious mixture by the internal mold form. The castable cementitious mixture further preferably includes a fibrous material, such as polypropylene fibers, for reinforcing the castable cementitious mixture.
The preferred step of mixing includes: adding water to a heated mixing apparatus; mixing the air entraining agent into the mixing apparatus until dispersed in the water; mixing the cement in the mixing apparatus until a cementitious slurry is formed; mixing the perlite into the cementitious slurry in the mixing apparatus until a cementitious perlite slurry is formed with entrained air; and mixing the fibrous material into the cementitious perlite slurry in the mixing apparatus, for forming the castable cementitious mixture. The perlite is preferably mixed into the cementitious slurry by feeding the perlite with a material feeding device.
The preferred method further includes a step of preparing the external mold form with a retarding/parting agent, for slowing curing of the castable cementitious mixture at an outer surface region of the article and for facilitating separation of the external mold form from the article. The external mold form liner is preferably made of a light weight flexible material such that the external mold form can be unfolded and prepared with the retarding/parting agent. The preferred method further includes preparing the internal mold form with a parting agent, such as a plastic film, that also prevents crazing of the castable cementitious mixture upon curing.
The present invention also features a method for making an article with a decorative surface texture from a cementitious composition. The method comprises the steps of: mixing a castable cementitious mixture including an aqueous slurry of at least cement and perlite; preparing a surface of the mold with a retarding agent; pouring a quantity of the castable cementitious mixture into a mold; casting the castable cementitious mixture in the mold until the castable cementitious mixture substantially cures to form the article; and removing the article from the mold. The retarding agent slows down curing of the article at an external surface region of the article such that the perlite and concrete form a decorative surface texture. This method preferably includes a further step of finishing the outer surface of the region of the article upon removal of the article from the mold.
One embodiment of the retarding agent includes a mixture of at least water, sugar and glue. The preferred embodiment of the retarding agent further includes a solvent alcohol in the mixture.
One example of the retarding agent further includes a pigment for indicating a density of application of the agent and a degree of penetration of the retarding agent. The glue includes either white or yellow glue and preferably both.
A decorative molded article made according to this method includes a body portion formed when the castable cementitious mixture cures between the external and internal mold forms. The body portion includes a plurality of walls defining a hollow internal region, for covering a structure, such as a utility installation. At least one of the plurality of walls includes an outer surface region having a decorative texture. According to various embodiments of the hollow, decorative article, the body portion further includes one or more apertures extending through one or more of the plurality of walls, for venting the hollow region of the body portion. The article can also include a recessed top region, for receiving water and/or earth material, or a flat, peaked or domed top region.